I heard that Diego Rivera used Chinese brushes to paint his frescoes. Therefore, I bought a bunch of those soft haired brushes to paint with. Later I added a few stiff nylon watercolor brushes. People who used these brushes compared painting into fresco to watercolor:
Gonzalo preferred to use his own bristle brushes when he painted on wet fresco. I believe that Jose Galindo taught us with bristle brushes, because I remember having a stiff control over the fresco painting:
Ultimately one can probably use most any brush to paint on fresco, and might experiment. The artist could make longer lines with a brush made with human hair, like he would with a striping brush. I wonder how yucca brushes would work in lime, after their tips were chewed down into fibers, to paint with.